Question

how will the level of carbon in the atmosphere change if humans do nothing to reduce their impact on the carbon cycle?
carbon will be removed from the atmosphere altogether.
the level of carbon in the atmosphere will decrease.
carbon in the atmosphere will remain the same.
the level of carbon in the atmosphere will increase.

Explanation:

Currently, human activities like burning fossil - fuels release carbon into the atmosphere. If no action is taken to reduce human impact on the carbon cycle, more carbon will be added, increasing its atmospheric level.

Answer:

The level of carbon in the atmosphere will increase.